Leaf miner: identify, prevent, control

Most active in warm weather on soft new growth, October to April.

Leaf miners are the larvae of small flies or moths that tunnel between the upper and lower leaf surfaces. They leave winding pale trails through leaves of citrus, beet, silverbeet and tomato, and while damage looks alarming it rarely kills established plants.

How to identify it

• Winding white or pale squiggly trails through the leaf
• Blotchy pale patches where several mines join up
• Curled, silvered new growth on citrus from the citrus leaf miner
• Tiny larvae visible inside the mine when held to the light

How to prevent it

• Remove and bin affected leaves promptly to stop larvae maturing
• Cover susceptible crops with fine netting to keep egg-laying adults off
• Keep plants vigorous so they tolerate some mining without major loss
• Clear weeds like dock and fat hen that host leaf miners

Organic control, step by step

• Squash larvae inside the mines by pressing along the trail
• Pick off and bin the worst-affected leaves
• Spray eco-oil on new citrus flushes to deter citrus leaf miner egg-laying
• Time oil sprays to protect soft new growth, repeating every 5 to 7 days during a flush
• Encourage parasitic wasps, which are the main natural control, by avoiding broad-spectrum sprays

Plants it attacks